In recent years, from the viewpoint of environmental protection, any electrical devices have been controlled by an inverter circuit for promoting energy saving and achieving high efficiency. Particularly, in the automobile industry, technologies, which are eco-friendly and relate to energy saving and high efficiency, have been developed actively. For example, a hybrid electric vehicle (hereinafter, referred to as “HEV”), which runs on an electric motor and an engine, has been introduced into the market.
Since a range of working voltage of electric motors used in HEVs is as high as several hundred volts, as capacitors used for such motors, much attention has been paid to metallized film capacitors having electrical characteristics of high withstand voltage and low loss. Furthermore, also in response to the market demand for maintenance-free products, metallized film capacitors having an extremely long life-time have been tended to be employed.
A metallized film capacitor used for HEVs is required to have external-environmental resistance, such as moisture resistance and heat resistance, for the reason of, for example, places to be disposed. Therefore, in general, the metallized film capacitor is used in a state in which plural metallized film capacitors connected in parallel with bus bars is stored in a case, and mold resin is input into the case. The mold resin input in this way protects the metallized film capacitors from infiltration by moisture or influence by heat from the outside.
A conventional configuration of a case-mold-type capacitor housing such a metallized film capacitor is described using a case-mold-type capacitor disclosed in PTL 1 as an example. FIG. 12 is a perspective view of the case-mold-type capacitor disclosed in PTL 1.
In case-mold-type capacitor 101, bus bars 102, 103, 104, and 105 made of, for example, copper plates are connected to both edge surfaces of a metallized film capacitor element, and the metallized film capacitor element and bus bars 102, 103, 104, and 105 are accommodated in a housing portion of case 106 having an upper surface opening. The housing portion of case 106 is filled with mold resin 107, so that the metallized film capacitor element is protected from outer environment.
In ordinary usage, case-mold-type capacitor 101 is housed in the metal case, and connected to other components separately housed. Therefore, bus bars 102, 103, 104, and 105 connected to the other component are required to be disposed with high dimensional accuracy. In particular, it becomes important to improve dimensional accuracy between the adjacent bus bars (between bus bar 102 and bus bar 103, and between bus bar 104 and bus bar 105). However, it is difficult to dispose bus bars 102, 103, 104, and 105 to the same positions without error, and it is difficult to unify all the distances between adjacent bus bars in plural case-mold-type capacitors 101.
In order to solve this problem, PTL 2 discloses the following structure. FIG. 13A shows bus bar 201 disclosed in PTL 2. FIG. 13B shows a metallized film capacitor element and bus bar 201 housed in case 202 disclosed in PTL 2.
As shown in FIG. 13A, bus bar 201 includes common connection portion 203 between terminal portions 201a and 201b for external connection of bus bar 201. Bus bar 201 including common connection portion 203 is attached to a metallized film capacitor element, and then housed in case 202 together with the metallized film capacitor element, as shown in FIG. 13B. Finally, case 202 is filled with mold resin 204, and common connection portion 203 is cut off and removed with a jig, such as a nipper. Thus, a case-mold-type capacitor is completed.
That is to say, in a technique disclosed in PTL 2, instead of attaching independently separated bus bars to the metallized film capacitor element, bus bar 201 in which terminal portions 201a and 201b are integrated by common connection portion 203 is attached to the metallized film capacitor element, and common connection portion 203 is then cut off and removed with a cutting tool, such as a nipper. Thus, conventional errors in dimensional accuracy between terminals, occurring when independently separated bus bars are attached to the metallized film capacitor element, are suppressed.